The invention relates generally to data recovery of storage technologies, and more particularly to methods, apparatuses and systems for data recovery by adaptive and selective level conditioning and data recognition of a read channel of storage technologies.
Advances in manufacturing technologies and system architecture have led to increasingly powerful consumer electronic devices and computers. These consumer electronic devices and computers support features and applications, such as multimedia, in connection with which vast amounts of information are processed and stored. Generally, the amount of information is not only vast, but also ever-increasing.
To provide the information, storage technologies have been developed, including magnetic, optical and magneto-optical technologies. Although these technologies provide relatively large storage capabilities, the technologies generally demand ongoing improvement so as to overcome factors limiting storage capacity. Among other areas for ongoing improvement is the accurate detection of recorded data, particularly while increasing the recording density.
Detection of recorded data is conventionally accomplished using a threshold. As an example, channel bits of an optical read channel (using, for example, 1,7 run-length-limited modulation coding) are detected by comparing a read signal to a predetermined threshold: if the read signal exceeds the threshold at a particular channel-bit location, that channel-bit is considered a `1` (i.e., a mark); otherwise the channel-bit is considered a `0` (i.e., a space).
Detection against a threshold typically relies on setting an appropriate threshold. Generally, the threshold is set toward recovering recorded information within an acceptable bit error rate. To do so, the threshold optimally is set to the center of an "eye-pattern", the eye-pattern being a measure that indicates the amplitude and phase margins of the read signal. However, the read signal's amplitude and phase margins tend to be affected by various parameters, including, among others, the write power, the write sensitivity of the media, the quality of the spot of the write and read drives (e.g., mark size variations), the focus offset of the write and read drives, and the recording density. For example, increased recording density tends to increase inter-symbol interference ("ISI") such that amplitude margins can degrade as to both marks and spaces. Moreover, because these parameters vary across systems and media, the center of the eye pattern tends to vary and, in turn, the optimal threshold setting tends to vary.
When reading channel bits of an optical channel, using any one of a plurality of coding methodologies, the correct data patterns must follow prescribed rules and protocol. For example, using 1,7 run length limited modulation coding, the highest frequency possible consists of 2T marks on space (where T=one channel bit period). Due to optical aberrations, interference, and other data reading complications, information read from optical drive occasionally does not comply with these prescribed rules, creating data reading errors.
Accordingly, it is desirable to provide for accurate detection of recorded data while accommodating increased recording density and other parameters that tend to cause the threshold to vary and margins to degrade. Further, it is desirable to insure compliance with the data coding rules for the type of recording protocol used.